Report: This literature review first presents the credit constraints faced by small and medium firms and the instruments that could be implemented to reduce such constraints. In this first part, we also present different impact evaluation methods and describe the ones that could be used for the different instruments above mentioned. We then review three types of instruments which are often implemented: credit lines, guarantee mechanisms and investment funds. For each of these instruments, we present its aims and objectives, as well as the way to evaluate it. We also expose the results of some evaluations previously conducted and available in the literature. For each instrument, we also highlight some specific insights and potentially useful for the French Agency of Development.